July 6, 2010

Progressive lenses, which are also referred to as invisible bifocals, graduated prescription lenses, and varifocal or multifocal lenses, are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient of increasing lens power, added to the wearer’s correction for the other refractive errors. Nowadays, there are hundreds of types and brands of progressive lenses on the market. Some of these lens designs can be 20-30 years old. In the past few years, there have been huge advancements in the world of progressive lenses. Among all type of progressive lenses. The best generation of progressive lenses is called free-form progressive lenses. Thanks to the introduction of Free Form surfacing to the lens manufacturing process,the Optical Industry is poised for significant change.The transition to Free Form Technology is a watershed in the history of eyewear, much like the transition from Bifocals to the original progressive lenses.It is a computer-aided design and manufacturing process, not a lens type.

Free Form progressives stems from by deciding on an ideal or target optical performance for the lens design for the given prescription. Using computer ray tracing and lens-eye modeling the actual optical performance can then be determined, finally complex state-of-the-art computer generated algorithms map out the surface of the lens to achieve an optimized optical performance by minimizing the differences between the target optical performance of the design and the actual optical performance.Compare with traditional progressive lenses,the Free Form Progressive have the following advantages:

a. The lenses are easier to adapt to given their extremely low aberration level and smooth transition.
b. Wider field of vision at all distances because the progressive surface is closer to the eye. The intermediate and near visual fields are up to 35% larger than conventional Progressive lenses. They will ensure the widest fields of vision in comparison to traditional progressive lens manufacturing. With a Rear Surface progressive, as much as 50% larger viewing zones will be achieved.
c. Immediate adaptation due to reduced dizziness and balance problems. Great for wearers changing from Bifocals to Progressives.
d. Quicker adaptation thanks to optimal design ergonomics that fully respect the routine movements of new progressive wearers and wearers of progressive lenses with a different design.

And the biggest advantage with free-form progressive eyeglasses is that they are customized to the individual. In the past progressive lenses could only be made from lenses with certain pre-determined base curves, which gave sub-optimal optics. Because free-form progressives are customized to your individual prescription and frame parameters they increase your field of view and decrease distortions in the periphery of the lens. Distortions in the periphery of the lenses were always a disadvantage with traditional progressive lenses and contributed to adaptation problems.

The free form progressive glasses are a bit more expensive than traditional progressive lenses, but in our opinions, the benefits outweigh the cost more.
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